I can answer the PS part of your question. You can mulch this grass over the winter, and it will provide a small level of protection. My favorite way to do it is with small pine branches, which are piled loosely on top and then filled with fall leaves. Once it's all covered with snowfall, it does a pretty good job of insulating the soil beneath. Be sure to remove it all in late winter, so the leaves won't start rotting as the weather warms.

thanks for the tips!

I am growing several other cultivars of Japanese forest grass aka Hakonechloa macra and they do just fine over the winter up here in zone 3/4. We have great snow cover BUT the plants also had no trouble surviving a winter in our old zone 5 garden with unreliable snow cover. I never did bother mulching.
HOWEVER, I think I would wait & buy your plants in the spring or .... if you are getting a good deal, do go ahead & buy them now but, protect them well for this winter until they get established.
A